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Positive Feedback ISSUE 53
Ground Disruptor Blue Dot and the Pulse Gen ZX
as reviewed by John Hoffman
Many savvy audio hobbyists are aware of the detrimental effects of power grid noise, and the effect it has on audio reproduction. The textbook solution is to install a power conditioner, although the products available do have varying degrees of effectiveness. Current production conditioners have a wide array of solutions for combating power grid noise, such as isolation transformers, AC regeneration, or cancellation circuits. Since conditioners have varying degrees of operation, the question that needs to be asked is: "exactly what is power grid noise, and how does it get into the system?" This month I posed this question to Jerry Ramsey at Audio Magic, and received a very informative answer. Jerry and I spent at least forty five minutes talking about the types of power grid noise, and the effects it has on audio reproduction.
There are three main categories of power grid noise, and each one requires a different solution to minimize its effects. Line noise is the primary type of power grid noise that the hobbyist is aware of, and the transmission pathway is the AC plug that audio components are connected to. Unfortunately for audiophiles the AC pathway is not a single purpose device, but has been harnessed to carry out a wide variety of tasks. Embedded within the power grid is an array of power line communication signals, and these protocols operate at many different frequency bands. Some of these signals provide remote recording of power meter readings, monitoring the internal operation of the grid, BPL (Broad Band over Power line) Internet service, and household automation programs that can be executed through the AC line. The majority of these communication signals operate outside the bandwidth of an audio system, although there are certain carrier signals that operate between 15 to 20kHz range. These signals will overlap with the upper range of an audio system, and have a detrimental effect on the quality of audio playback.
RFI and EMF is another form of audio noise which is an unavoidable effect due to the physical layout of the power grid. Miles of unshielded power line function as an antennae, and provide a pathway for radio frequency interference to enter an audio system. Large power transformers at substations are used to push the power down the lines, but also create their own electro-magnetic fields which affect the current passing through them. Electric companies are not going to optimize the power grid for audio hobbyists, so the only solution is to clean the incoming household current of the effects of RFI/EMF.
Whether it is a farm in the country, a manufacturing plant across town, or a single house in a suburb, all of these consumers are linked together through the electrical grid ground line. In a house there is a ground rod for the fuse box, but this does not uncouple the home's electrical system from the power grid. There is a significant amount of noise that rides on the ground plane, and it will have an audible effect on the performance of an audio system. There are thousands of small motors in home appliances spread throughout the grid, and each one of them is putting an electrical back pulse into the ground line. Manufacturing facilities are major consumers of power, and contribute to ground line pollution significantly. The large motors used in these plants have exponentially larger back pulses, and certainly add to the pollution of the power grid ground line as well. There are other ways that the ground side of the power grid can be compromised, but these are two examples that affect virtually any town across the country.
The effects of different types of power grid noise are markedly similar, even though they have different root causes. Power grid noise will lower the resolution of an audio system by masking low level detail, smearing the layering in the sound stage, and producing edginess and grunge in high frequencies. Since each type of power line noise has a different composition, there is not a single product that can effectively eliminate all of them. Jerry Ramsey has developed a series of products that can combat each type of noise, and are intended to be used in conjunction with each other in a system. My reference system currently contains the Audio Magic Mini Reference power conditioner, the Pulse Gen Module, and the Speaker Clarifier Modules. Each component has been added to the system in the same chronological order as referenced. There has been a cumulative effect of these products, but I was missing the final piece of the Audio Magic package. Jerry just released an enhanced version of a ground filter which is the Ground Disrupter Blue Dot. The Blue Dot has a price tag of $700, which places it in the middle of the price range of the Audio Magic power conditioning product line.
The Ground Disrupter Blue Dot deals with ground noise in two different steps. This module contains two different ground planes that are designed to funnel ground noise through two passive filter devices. The Blue Dot also contains a Pulse Gen Module, which cancels RFI/EMF noise that rides on the ground plane of audio components. Since the Pulse Gen Module is an active device, the Blue Dot does need to be plugged into a power outlet. I connected the Blue Dot straight to the wall, and then moved it to my power conditioner. The performance of the unit improved minimally when ran through the conditioner, but the unit certainly does the job when connected straight to the wall. A single RCA cable comes out of the Blue Dot and needs to be hooked up to an unused RCA input in the system. I have an unused input on my Electra Print PVA preamp, so connecting the Blue Dot was not difficult at all. The Pulse Gen module needs a couple of hours to warm up and stabilize, but an evening listening session was all that was needed to get the Blue Dot working properly.
The Blue Dot definitely affects the placement of instruments and performers in the sound stage. "Come On Come On" is the title track to a Mary Chapin Carpenter [Come On Come On; Columbia CK 48881] disc that gets a great deal of playing time on my system. On this song, the back up vocals are located on the corners of the sound stage. With my current speakers these vocals were always laying on the plane of the speaker, which is an attribute that appeared to be a result of the dispersion characteristics of Sachiko double horn and the Fostex full range driver. Other speakers I have had in the house did not exhibit this characteristic, or at least to this degree. I could only assume that this was related to the tall front baffle and the beaming effects of the eight inch driver. However, when I installed the Blue Dot, the music underwent a noticeable transformation. First of all, the lower registers of Carpenter's voice filled in, and became vibrant and rich. Also, the acoustic guitar gained body, and the clarity of the instrument increased. What really stood out was the change in the location of the back up vocals. The voices were no longer laying against the face of the speaker, but have moved out a good two feet into the room. After this disc I had no doubt about the effect of the this Ground Disruptor on my system—at least on this disc. Now the focus of my listening sessions was to discover if the effects of this module were going to be consistent and repeatable.
Another significant contribution of the Blue Dot in my system is the removal of high frequency glare. The addition of the Ground Disrupter results in a smoother presentation of the music, but without a reduction of low level detail. This attribute became readily apparent when I spent some time listening to an Allison Krause disc. The song "Now That I Found You" [Now That I Found You; Rounder CD 0325] has a great deal of high frequency information, and this song often appears to have a brittle quality to its presentation. In previous listening sessions, the mandolin and acoustic guitars have an edginess and glare to their sound. With the Blue Dot installed into the system, these instruments become relaxed, and gain a noticeable degree of refinement. Overall, the character of the music gains a natural flow, and moves closer to presentation of a live performance. One point that I want to reiterate is that the Blue Dot does not artificially strip the music of high frequency information, but is only removing the effects of power grid noise. The end result is the Blue Dot brings the tonal structure of the upper octaves into proper balance.
Audio hobbyists often overlook the ability of an audio system to recreate the ebb and flow of music. Another descriptor for this event is PRAT (Pace, Rhythm, and Timing), which is an attribute that many European audiophiles pay very close attention to. I have discovered over the years that the isolation and tuning devices that are prevalent in this hobby often affect PRAT in a negative manner. Many of these devices alter frequency bands where power grid noise is concentrated, which makes them appear to have a positive effect on the music. Unfortunately the ebb and flow of the music is altered, which gives the audio system a wholly unnatural presentation. The Audio Magic Blue Dot is unusual in that PRAT is not negatively affected, but is actually easier to experience since the noise floor of a system is lowered. For instance, the bass line on "Ruby" [Window Wide Open; Self Released] by Shannon Beck undergoes a wonderful transformation when the Ground Disrupter is installed. The bass guitar becomes clearly defined, and has a natural flow to its part. The acoustic guitar that carries the melody gains clarity and definition, yet the interplay between both guitars is seamless in its presentation. Every aspect of this song is now in proper time, and the Blue Dot steadfastly preserves this relationship.
A great deal of the mysticism of power line noise has been debunked over the past decade. No longer is the problem viewed as a singular event, but instead as a holistic issue with multiple points of entry into an audio system. A fully developed noise suppression strategy will address not only the power mains signal, but also the effects or airborne RFI/EMF, and isolation of the ground line that a system is tethered to. Jerry Ramsey of Audio Magic has developed an array of products that are effective at neutralizing power grid noise at several different levels. In a step by step process I have added several Audio Magic power conditioning products to my system, and each device has resulted in a noticeable advancement of performance. Each Audio Magic component attacks noise in a different manner, but the end result is a greater degree of clarity, an improved definition of space within the recording, and an uncovering of the dynamic contrasts contained within the music. The Ground Disruptor Blue Dot continued this trend, and brought yet another degree of refinement to my system. There was significant improvements in both the tonal and spatial aspects of the recording, in spite of the fact that the other modules were already in the system and performing their assigned tasks. The Audio Magic power conditioning products are an effective tool for combating power grid noise. Clean AC power is an excellent foundation on which to build a system on, and provides a safe pathway for achieving satisfying music reproduction.
Audio Magic Pulse Gen: The Analog Application
The effects of RFI/EMF can certainly compromise the sound quality of an analog system. The primary pathway for this type of noise to enter the system is the tonearm wiring. The traditional method of solving this issue is to use a heavily shielded tone arm cable, and in the past that was often considered good enough. The performance of turntable motors and phono stages can be improved by the use of a power conditioner, and result in a lower system noise floor. While both of these techniques have merit, there is another manner to improve analog performance that I have recently encountered.
The Audio Magic Pulse Gen module performs extremely well in my DAC, and I wondered if it could have the same effect on my analog system. My current phono stage is the Liberty B2B-1, which is a nicely executed circuit with a remarkably low noise floor. Yet I had to wonder if there were performance gains that could still be realized, so Jerry Ramsey sent off a module for me to evaluate.
The latest generation of the Pule Gen module now has a ground cable, which extends the effect of the module into the ground plane of a component. Installation was straight forward, and this wire was lightly soldered to the ground tab on the RCA output jack. There is not enough room in the chassis to mount the box, so the alternate installation option is to locate the module right against the RCA output cables. In my previous experience, the module took a couple of hours to warm up, and twenty-four hours to reach its full effectiveness. In this application the Pulse Gen followed the same warm-up curve, and performed exactly like its predecessor.
My analog system consists of a Galibier Audio Serac turntable which uses a battery driven DC motor. The tonearm is an Audio Artisan, that is fitted with a Discovery Audio tonearm cable. An Accuphase AC3 currently hangs off the arm, and this is a .20mv output moving coil cartridge. The phono stage is the aforementioned Liberty Audio B2B-1, which is equipped to drive low output cartridges. This combination has a low noise floor, although the use of an LOMC cartridge presents a significant challenge in the battle to maintain signal purity.
The Pulse Gen module sells for $400, which means it is a significant investment for an accessory. Although when you look at the price range of analog gizmos these days, the cost of the Pulse Gen becomes somewhat of a bargain. From my perspective analog pricing has got out of hand; $300 digital scales and $500 record clamps shatter the definition of what affordable audio is. When the effects of this module are evaluated, the price tag becomes downright reasonable.
The Pulse Gen module has a significant impact in this application. Based on its effects, I can say with a great deal of confidence that the effects of RFI/EMF are a notable issue with analog playback. When listening to "Rain Dance' [Winter Into Spring; Windham Hill WH1019] by George Winston, I was impressed with the increase in clarity and definition of the music. Piano notes became clearly defined, and the decay of individual notes improved markedly. The dynamic contrasts contained in the song grew in strength, and resulted in a presentation that is significantly closer to a real instrument. When the module was removed, the music became smeared, and the realistic feel to the piano was completely lost. Also the edges of the sound stage became hazy, and the definition of the recording venue could not be as easily recognized.
The George Winston album is a solo instrument recording, so the next step was to evaluate the module on more complex music. "A Rock For The Forgotten" [Boomtown; A&M Records SP5134] by David and David is an example of a properly executed modern studio recording, and the Pulse Gen module still works its magic on this song. Background instruments and sound effects that are mixed into the song are easier to hear, and are clearly formed. The separation between the two vocalists on the chorus is easier to perceive, yet the blending of the two voices gains color and texture. The electric bass guitar now has greater authority, and the punch of each note increases in power. Once again every aspect of the music improved, and these gains can be directly related to the Pulse Gen module.
The contribution of the Pulse Gen module is remarkably consistent, and results in noticeable gains in performance of my analog system. The improvement in sound quality is unique in how it is achieved, and it cannot be realized by upgrading other components in the analog chain. It does not matter if the vinyl playback system is a modest combination, or a multi kilo buck high performance rig, the Pulse Gen module still has a place in either arrangement. I can wholeheartedly recommend its use, once you hear the effects I think you will have a difficult time living without it. John Hoffman
Ground Disruptor Blue Dot